1. Field of the Invention
The present invention generally relates to semiconductor manufacturing and more particularly to an improved system and methodology for controlling film thicknesses.
2. Description of the Related Art
Conventional semiconductor fabrication process control is based on normal statistical distribution methodologies. Conventional logic considers that all variation in process is random; wafer-to-wafer, run-to-run, and within wafer variations. However, conventional processes regularly produce a thickness pattern which introduces intrinsic variability to the measured average film thickness. The invention described below improves upon the conventional methodology of controlling film thickness variations.